Characterisation of precipitation and carbide coarsening in low carbon alloy Q&T steel during the early stages of tempering

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@article{511d26078f3540038b2ca629cab4ca4c,
title = "Characterisation of precipitation and carbide coarsening in low carbon alloy Q&T steel during the early stages of tempering",
abstract = "In order to ensure that appropriate tempering conditions are used to obtain desired strength and toughness for low carbon low alloy quench and tempered (Q&T) steel plates in a range of thickness, it is desirable to be able to predict the effect of composition and tempering conditions (time and temperature) on the microstructure and hence the hardness evolution for these steels. In this paper, carbide precipitation and coarsening behaviour in three low carbon low alloy Q&T steels have been investigated during tempering at 600 °C up to 16 h to determine the role of alloying additions of Mo, V, Cr and Si. It has been found that auto-tempering occurs during water quenching with ε{\textquoteright}-carbide and cementite being present within the martensite laths for all three steels. In the Base steel, cementite becomes the stable second phase after 2 h tempering and has an elliptical (sometimes spherical) shape, which coarsens with time during tempering from 2 h to 16 h. However, in the Base-Mo-V and Base-Cr-Mo-V-Si steels, elliptical and needle-shaped cementite (shown to contain Mn, Mo and Cr) both exist during tempering; furthermore, finer elliptical secondary Mo-V-rich carbides are observed after tempering for 4 h. The coarsening of cementite contributing to the softening process in the three steels has been quantified with, most significantly, the inter- and intra-lath carbides coarsening independently. Although fine secondary alloy carbides are observed after 4 h tempering, they do not result in any noticeable secondary hardening peak in the Base-Mo-V and Base-Cr-Mo-V-Si steels.",
author = "Yulin Ju and Martin Strangwood and Claire Davis and Aimee Goodall",
year = "2018",
month = dec,
day = "19",
doi = "10.1016/j.msea.2018.09.044",
language = "English",
volume = "738",
pages = "174--189",
journal = "Materials Science and Engineering A",
issn = "0921-5093",
publisher = "Elsevier",

}

RIS

TY - JOUR

T1 - Characterisation of precipitation and carbide coarsening in low carbon alloy Q&T steel during the early stages of tempering

AU - Ju, Yulin

AU - Strangwood, Martin

AU - Davis, Claire

AU - Goodall, Aimee

PY - 2018/12/19

Y1 - 2018/12/19

N2 - In order to ensure that appropriate tempering conditions are used to obtain desired strength and toughness for low carbon low alloy quench and tempered (Q&T) steel plates in a range of thickness, it is desirable to be able to predict the effect of composition and tempering conditions (time and temperature) on the microstructure and hence the hardness evolution for these steels. In this paper, carbide precipitation and coarsening behaviour in three low carbon low alloy Q&T steels have been investigated during tempering at 600 °C up to 16 h to determine the role of alloying additions of Mo, V, Cr and Si. It has been found that auto-tempering occurs during water quenching with ε’-carbide and cementite being present within the martensite laths for all three steels. In the Base steel, cementite becomes the stable second phase after 2 h tempering and has an elliptical (sometimes spherical) shape, which coarsens with time during tempering from 2 h to 16 h. However, in the Base-Mo-V and Base-Cr-Mo-V-Si steels, elliptical and needle-shaped cementite (shown to contain Mn, Mo and Cr) both exist during tempering; furthermore, finer elliptical secondary Mo-V-rich carbides are observed after tempering for 4 h. The coarsening of cementite contributing to the softening process in the three steels has been quantified with, most significantly, the inter- and intra-lath carbides coarsening independently. Although fine secondary alloy carbides are observed after 4 h tempering, they do not result in any noticeable secondary hardening peak in the Base-Mo-V and Base-Cr-Mo-V-Si steels.

AB - In order to ensure that appropriate tempering conditions are used to obtain desired strength and toughness for low carbon low alloy quench and tempered (Q&T) steel plates in a range of thickness, it is desirable to be able to predict the effect of composition and tempering conditions (time and temperature) on the microstructure and hence the hardness evolution for these steels. In this paper, carbide precipitation and coarsening behaviour in three low carbon low alloy Q&T steels have been investigated during tempering at 600 °C up to 16 h to determine the role of alloying additions of Mo, V, Cr and Si. It has been found that auto-tempering occurs during water quenching with ε’-carbide and cementite being present within the martensite laths for all three steels. In the Base steel, cementite becomes the stable second phase after 2 h tempering and has an elliptical (sometimes spherical) shape, which coarsens with time during tempering from 2 h to 16 h. However, in the Base-Mo-V and Base-Cr-Mo-V-Si steels, elliptical and needle-shaped cementite (shown to contain Mn, Mo and Cr) both exist during tempering; furthermore, finer elliptical secondary Mo-V-rich carbides are observed after tempering for 4 h. The coarsening of cementite contributing to the softening process in the three steels has been quantified with, most significantly, the inter- and intra-lath carbides coarsening independently. Although fine secondary alloy carbides are observed after 4 h tempering, they do not result in any noticeable secondary hardening peak in the Base-Mo-V and Base-Cr-Mo-V-Si steels.

U2 - 10.1016/j.msea.2018.09.044

DO - 10.1016/j.msea.2018.09.044

M3 - Article

VL - 738

SP - 174

EP - 189

JO - Materials Science and Engineering A

JF - Materials Science and Engineering A

SN - 0921-5093

ER -